Semiconductor lasers are widely used in a variety of applications including optical navigation systems (ONS) used to track movement of the ONS relative to a surface. One type of ONS increasingly used in, for example, optical computer mice may be a speckle-based ONS. In a speckle-based ONS, movement between the system and the surface may be sensed based on displacement of a complex intensity distribution pattern, known as speckle, which may be generated by scattering coherent light from a semiconductor laser off an optically rough surface. Because speckle may be produced by interference of reflected light, speckle-based ONSs are polarization and/or frequency sensitive such that a shift in a state of polarization (SOP) of the laser could result in an abrupt, erroneous indication of movement. For this reason, semiconductor lasers used in such applications must have a stable fixed SOP.
One type of semiconductor laser frequently used in speckle-based ONS's may be a vertical cavity surface-emitting laser (VCSEL). VCSEL's are used due to their lower manufacturing costs, reliability, and symmetrical optical output. VCSELs are manufactured by forming two distributed Bragg reflector mirrors, each including multiple layers of alternating materials with varying refractive index on a semiconductor substrate. Laser beams are emitted perpendicular from a top surface of the VCSEL and are polarized along crystallographic planes of the layers. As a result, VCSELs can quickly switch states of polarization and/or emit light simultaneously from multiple SOPs. Conventional approaches to solving SOP switching or hopping include using polarization stabilized VCSEL's, which typically have higher cost.